Packages allowing significant penetration of oxygen or other gases are undesirable where gas transmission contributes to the decay of the packaged product. For example, the development of packages having low oxygen transmission rates, i.e. high oxygen barrier properties, has long been a desirable objective in the food packaging industry, because low gas permeability food packages increase the shelf life of the packaged food products. Packages having low oxygen transmission rates also have utility for packaging other oxygen sensitive materials, such as oxygen activated sealants. Longer shelf life of the product increases inventory efficiency for distributors, and reduces the likelihood that the consumer will accidently purchase a contaminated product. For a plastic film to be qualified for food packaging applications, therefore, the film has to have low oxygen permeability not only at low relative humidity, but also at high relative humidity since the packed food may be stored in the high humidity environment. Unfortunately most of the commercially available plastic film cannot meet these two requirements simultaneously. The ideal film will have both low oxygen permeability and will be insensitive to relative humidity. The present invention solves these problems by teaching a silicone treated plastic film which exhibits excellent low gas transmission characteristics both at 0% relative humidity and at 85% relative humidity.
U.S. Pat. Nos. 5,077,135 and 5,096,738 to Wyman disclose a method of imbuing polymer films with gas impermeable surface characteristics using a silane compound and cross-linking same, while providing physical adsorption adherence to the film and with sufficient coating to produce gas and related barrier characteristics. However, the present invention is distinguishable from the '135 and '738 patents because the present invention teaches a silane which is cured by ultraviolet radiation rather than electron beam irradiation, which is taught as the cure method in the '135 and '738 patents.